Self-locking nut



June 18, 1946. M, QA TAN 2,402,159

SELF-LOCKING NUT Filed Oct. 14, 1944 INVENTOR. MARK /7I47'T4/v Patented Jude 1a, 1946 UNITED STATES PATENT OFFICE SELF-LOCKING NUT Mark Hattan, Dayton, Ohio Application October 14, 1944, Serial No. 558,707

iGranted undoithe d of March a, 1883, as amended April so, 1928; 3'10 0. G. 751) 3 Claims.

1 The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon, 1

This invention relates to lock nuts, and amon other objects, aims to provide a constant torque self-locking nut of the type disclosed in my Dendin: application Serial No. 522,081 filed February 12, 1944, entitled Self-locking nut." The object of the invention is to provide an improved type of coiled wire for the thread and nut-locking means of the lock nut. In accordance with the invention, the resilient spirally coiled wire in the nut casing has waves or deformations which extend radially inwardly or at right angles to the axis of the spiral, and which are adapted to be flattened when the lock nut is screwed on a stud or bolt, thereby to lock the lock nut in any position.

The above and other objects and advantages will be understood after referring to the following detailed description of a preferred embodiment of the invention, taken in connection with the accompanying drawing, in which:

Fi l is a top plan view of the nut body per se;

Fig. 2 is a side elevation of the same;

Fig. 3 is a half section of the same on line 3-4 of Fig. 1;

Fig. 4 is a half section of the nut body with the locking spring in normal position;

Fig. 5 is an enlarged cross section of the nut with the locking spring; and

Fig. 6 is an enlarged cross section through the locking spring.

Referring particularl to the drawing, the preferred form of self-locking nut comprises 8. casing, shell or body ll whose exterior'side walls may be formed into a hexagon I I for a portion of the length of the nut and may have a plain, slightly frusto-conical portion I! for the remainder of the length. The circular edge I; of the frusto-conical portion is preferably chamfered and is adapted to be turned in by a spinning operation to form an annular end abutment or locking flange ll for holding the coiled locking spring ll after its insertion into the nut body. To facilitate the spinplug, a groove It is cut in the inner walls I! of the nut casing. The spring ii, which also provides a thread for the nut, snugly iits within the I smooth, cylindrical walls 11. At its bottom, the

nut casing has an annular flange-or shoulder it of uniform width but preferabl formed on its I 2 of substantiall the same dimensions andpitch as the locking spring and provides a stop or abutment'20 parallel to the axis of the nut, against which one extremity 24 of the coil spring l5 may press, under certain conditions. It will be clear that the locking spring is permanently secured within the body of the nut by the two abutments said seat being shown projecting from the nut,

although it need not do so. Cold pressing greatly increases the strength of the nut in the zone where the greatest stresses occur, and much higher loads may be imposed without failure; This zone of increased strength is indicated by the stippling 23 in Fig. 4. a

The locking spring ma be formed from stainless steel, spring carbon steel, or phosphor bronze wire, preferably music wire, and preferably has a minimum of six convolutions, greater strength however'being obtained when eight convolutions are used as shown in Fig. 4. The wire is wound as tightly as possible, with nogaps, and its lower extremity is preferably rounded, as at 24, while its upper end is preferably ground oil! at right angles to the axis of-the coil. However the upper end need not be ground and the upper extremity of the wire may be like the lower extremity 24.

l The wire previous to coiling is formed as shown in Fig. 6 by drawing it through a die or rollers; this cold drawing increases the tensile strength of the wire to about 395,000 p. s. i; Referring to Fig. 6, the wire it has two substantially square corners its, Nib, and a pair of converging or beveled faces 15c, lid at an angle of to the faces lie, Iii, respectively. Joining the beveled faces is a narrow, slightly convex face Hg. In'

a standard thread (except for slight deformations upper surface I! with a forming tool to provide 7 a uniformly helical abutment for the end of the coiled locking spring. The helical surface I! is to be described) for engagement with standard threads on bolts. The center line of each wire section is preferably square with the axi of the coiled wire spring, although other dispositions of the wire are possible.

Referring to Fis. 5, the several convolutions o! the spirally coiled wire each have a plurality of lateral deformations, waves, .or bends 25, there being preferably three or four of these waves in each convolution. For a one-half inch nut, the amplitude or maximum deflection ofa wave from the normal spiral shape of the wire (measured on a. line perpendicular to the axis of the spiral) may amount to .005 in. where the overall diameter oi the coilof wire is approximately .6045 in. The crests oi the waves preferably extend inwardly of the root diameter of the threads of any bolt or stud for which thelock nut is designed. The waves in the several convolutlons preferably occur at the same angular positions, although if preferred the waves may be disaligned as viewed from the end 01' the .spring. j The purpose of these waves is to provide a locking grip on the bolt or stud, the lockin grip arising from the fact that the conventional bolt threads straighten out or "flatten" the waves when the nut is threaded on the bolt. By the expressions straighten out or flatten I mean that the waves or deformations are made to assume the form of segments of the helix into which wireened on the bolt threads effects a secure gripping of the threads. As the wave are formed in permanently resilient wire, any straightening of the waves is only temporary, and as soon as the nut is removed from the bolt, the waves resume their original form. The deformations or waves are easily formed in the wire as it is coiled.

When the described nut is threaded on a nut or stud, there will be a slight spiral shifting or helical creeping of the coiled wire, this shitting taking place in the direction of flange 28 when the nut is being screwed on and in the direction of abutment M when the nut is being unscrewed. lt-has been found that this slight movement of the coiled wire is indispensable to the proper functioning of the nut, because the increase in the length of the coiled wire as the waves flatten or straighten out must be accommodated. It will be understoodhowever, that the wire coil is securely locked against turning or rotation within the casing i6 hy'its engagement with the end abutments or flanges M, is.

It has been proposed in Patent l lo. 1,228,671 to E. R. Hibbard, dated June 5, 1917, to provide a nut lock in the form of a washer whose central aperture is provided with a radial slot and a single thread having waves or deformations at several points, these waves being flattened ii. e., made to assume the form oi segments of shells) when the nut is tightened on a bolt. However, the thread is integral with the relatively rigid washer body and hence is anchored throughout its length, therefore cannot creep helically, and lateral flexing of the waved or deformed portions is necessaril resisted by the body of the washer almostthe entire length of a nut having several convolutions of thread. The starting torque is low and once the nut is fully on the bolt the torque remains constant, which is believed to be a uniquecharacteristic of nuts embodying the invention. With my lock nut, the locking torque is effective without the necessity of having the bolt project one and one-half or two full threads through the nut, as required of other nuts. As

the torque is constant, the user can be sure the nut is in proper condition to lock. There is no variation in torque from 150 in. lb. down to ill in. lb. in fifteen removals as with other loci; nuts which wear out rapidly inuse. Less injuries to personnel are likely due to the constant torque feature. It desired, however, the torque can be varied (in different nuts) by varying'the deformation oi the wire as it is coiled. Furthermore. it is contemplated that the wave at the boltreceiving end of the nut may be of zero amplitude,

' so that the nut starts on the bolt with almost no 7 torque. If desired, the wave amplitudes may increase uniformly from zero at the bolt-receiving end to a maximum at the other end, which would give rise to maximum torque at the end of the nut-assembling operation.

The invention is advantageous because the nut may be of an inexpensive steel casing (which is easily spun) enclosing a beryllium copper or phosphor bronze or stainless steel or other corrosion-resisting wire, where the high expense of a solid stainless steel nut is unwarranted. High strength music wire suitable for use in the nuts may be purchased for twenty cents a pound and from one poundof wire the threads for 66-70 one-half inch nuts may be made. It is far easier" to coil wire and insert it in the nut bodies than to out threads in certain metals; such metals may therefore be used for the forming of the wire insert. Enserts of stainless steel should cost less than one cent per nut of the one-hall inch size.

As the spring locking action is. effective over Gil and can only take place to a very limited extent along the inner (unanchored) edge of the single thread.

In accordance with the invention, I provide a thirty-two areas (in the preferred form), there is no danger of the spring wire being stressed at any point near to its elastic limit. Because drawn wire is used for the thread on the nut, the thresd is much smoother than it it were out. The close fit between the walls of the casing and the sprint? insures a strong grip by the spring on the casin when loads are applied. due to the radial compo nent of force provided by the 30 angles on the thread faces. This radial component tends to expand the coil in the casing, thus causing the casino walls to take a considerable portion of the tension load on the nut. Whatever load is thus carriedby the casing walls will not he carried by the base, which is obviously advantageous.

Tests indicate that a nut embodying the invention maybe screwed on and removed. from a bolt more than times without material loss in locking efficiency. Use of nuts willthereicre effect great savings in production and in stccmd parts (inventory) and will greatly reduce main tenance of all sorts oieduipment and macl'iiner'y.

lock out which distributes the lockingaction over E The invention has, all the advantageous lectures either shoulder and being so fitted in thecasingthat it may have a slight helical creep but being held non-rotatable, and having an internal shape forming a thread to be threaded on a bolt or stud; each'convolution least one deformation which is wave-like; the amplitude of each wave-like deformation being measurable in a direction substantially at right ancies to the longitudinal axis of the spiral spring and the not being removable from the salt or stud in the conventional manner.

as look-nut comprising, in combination, a

a hollow casing having inwardl extending -shouL- ders at the top and bottom;- and a spring wire closely coiled into a spiral and inserted in the hollow casing and shaped to form a thread, said coiled'spring wire being in contact with the inner walls of the casing and also in contact with either of said shoulders, and being immovably ot the spring having at I,

held; except for a. slight helical creep which is permitted when the nut is threaded on a hell; or stud; each convolution'of the coiled spring wire having at least one wave-like deformation;

the crests of said wave-like deformations extending inwardly of the root diameter of the threads 0! any bolt or stud for which the nut is designed, when the nut is of! the bolt or stud, said wave-like deformations yielding as the nut is threaded on a bolt or stud and assuming the form of sections of the spiral formed by said spring wire, the lookout being removable from the bolt or stud in the conventional manner,

3. A locknut comprising, in combination, a hollow casing having inwardly extending shoulders at the top and bottom, at least one of these shoulders having a helical surface provided with a stop thereon; and a. spring wire closely coiled into a spiral andinserted in the hollow casin and being shaped on the inward art so as to form substantially .a standard thread, said coiled spring wire being in con t with the inner walls of the casing and also in contact with either of said shoulders, and being immovably held thereby except for, a slight r'nitted when the nut is threaded on a bolt or stud; each convolution of the coiled spring wire having at; least one wave-like deformation; the crests of said wave-like deformations extending inwardly of the root diameter of the threads of any bolt or stud for which the nut is designed, when'the nut is on the bolt or stud; said wavelike deformations yielding as the nut is threaded on a bolt or stud and assuming the form of sections oi the spiral formed by said spring wire, the locknut being removable from the bolt or stud in the conventional'manner.

helical creep which is per- 

